1. Field of the Invention
The present general inventive concept relates to a substrate processing apparatus, and more particularly, to a substrate processing apparatus which employs a ferrite core to enhance plasma generation efficiency.
2. Description of the Related Art
A semiconductor wafer or a substrate (hereinafter, “substrate”) for various display devices is produced by repetitiously performing various substrate treatment processes, such as deposition and etching of a thin film, on the substrate.
FIG. 1 is a cross-sectional view illustrating a conventional substrate processing apparatus, and FIG. 2 is a plan view illustrating the conventional processing apparatus.
A conventional substrate processing apparatus 100 comprises an upper vessel 111 and a lower vessel 112 coupled to each other. A space is defined by the two coupled vessels 111 and 112, and divided into an upper reaction space 113 and a lower reaction space 114 via partitions 121 and 122, respectively. After being injected into the upper reaction space 113 and the lower reaction space 114, a reaction gas is ionized to generate plasma therein. The upper and lower reaction spaces 113 and 114 are provided with an upper chuck 131 and a lower chuck 132, respectively. A substrate as a processing target is generally located only on the lower chuck 132. The conventional substrate processing apparatus 100 further comprises six toroidal ferrite cores 141 disposed circumferentially at equal intervals on a same plane at an intermediate position between the upper reaction space 113 and the lower reaction space 114. Each of the toroidal ferrite cores 141 has a coil 142 turned therearound such that the coil 142 around one ferrite core 141 is turned in an opposite direction to a turning direction of the coil 142 of an adjacent toroidal ferrite core 141 in order to cause adjacent toroidal ferrite cores 141 to generate induced electromotive forces having opposite phases.
The upper reaction space 113 and the lower reaction space 114 communicate with each other through a hole 152 formed in a tube 151 penetrating the center of each toroidal ferrite core 141. The reaction gas passes through the hole 152, each of which becomes a path of a discharge current. When processing the substrate, the coil 142 turned around each of the toroidal ferrite cores 141 acts as a primary side and the plasma acts as a secondary side so that a high frequency power applied to the coil 142 is transferred to the plasma of the secondary side. The induced electromotive forces generated by the adjacent toroidal ferrite cores 141 have a phase difference of 180 degrees with respect to each other, and a current path induced by the plasma constitutes a closed path through adjacent holes 152. Arrows of FIG. 2 indicate six electric currents induced between the adjacent holes 152.
In order to improve a plasma generation efficiency, it is necessary to form a path of the secondary side current induced by the plasma as a closed circuit. To this end, the conventional substrate processing apparatus 100 has the upper reaction space 113 and the lower reaction space 114. In the conventional processing apparatus 100, however, substrate processing is performed only on one side of the substrate, whereas plasma is generated on both sides, causing a reduction in plasma density and plasma generation efficiency.